A. Field of the Invention
This invention relates to the art of manufacturing ends for cans, such as, for example, ends that close off aluminum beverage cans, ends for cans containing human or animal foods, and ends for containers for consumer products such as tennis balls. The invention also relates to a press that is used to make can ends and the methods by which such a press operates to form an end out of a sheet or coil of stock material.
B. Description of Related Art
It is well known to draw and iron a sheet metal blank to make a thin-walled can body for packaging beverages, such as beer, fruit juice or carbonated beverages. In a typical manufacturing method for making a drawn and ironed can body, a circular disk or blank is cut from a sheet of light gauge metal (such as aluminum). The blank is then drawn into a shallow cup using conventional cup forming punch and die equipment. The cup is then transferred to a body maker or can forming station. The body maker draws and irons the side walls of the cup to approximately the desired height and forms dome or other features on the bottom of the can. After formation of the can by the body maker, the top edge of the can is trimmed. The can is transferred to a necking station, where neck and flange features are formed on the upper region of the can. The flange is used as an attachment feature for permitting the lid for the can, known as an xe2x80x9cendxe2x80x9d in the art, to be secured to the can.
The end is the subject of a different manufacturing process and involves specially developed machines and systems to manufacture such ends in mass quantities. Representative patents describing end manufacturing methods and presses used to make such ends include Buhrke, U.S. Pat. No. 4,106,422, and Herrmann, U.S. Pat. No. 3,888,199. After the ends are manufactured they are bagged in large stacks (known in the art as xe2x80x9csticksxe2x80x9d or xe2x80x9cin stick formxe2x80x9d) and sent to a site where the cans are filled with a food, beverage, or other product.
In the Buhrke ""442 patent, a sheet or web of end material is fed into a press. The sheet is pierced, notched, and lanced according to a predetermined pattern at longitudinally spaced intervals to define a series of identical individual can top blanks. The blanks are separated in the web from each other by substantial openings void regions, but linked together by flexible xe2x80x9clinksxe2x80x9d, that is, portions of the web material that connect the blanks together. See, e.g., FIGS. 1, 2 and 3 of the Buhrke ""422 patent. After the sheet has been so formed, the sheet is sent to a series of stations of a single progressive die that complete for formation of the end in the web or sheet of material. The web material and links act as a carrier of the blanks until the ends are cut out of the web, whereupon the ends are sent to edge curling and finishing stations within the press.
While the Buhrke system was put into practice and used for a period of years during the early 1980""s, it was prone to problems and ultimately unsuccessful. In particular, the void features formed in the sheet of material in the beginning of the operations in the press created an elastic condition when the sheet was indexed through the press, leading to registration problems between the sheet of material and downstream work stations that formed the closure and other features in the end. More specifically, the void features led to relative movement between various portions of the sheet when the indexing mechanism moved the sheet through the press, resulting in a mis-alignment between the tools of the work stations and the portion of the sheet containing an end in various states of completion. Furthermore, the machine had a relatively low metal realization since the design requires material to carry the ends through the press. The resulting down-time to change the position of the dies, slow speed of operation, poor quality of ends due to the misalignment, and overall maintenance and metal utilization problems experienced by machines made in accordance with the ""422 Buhrke patent eventually resulted in the abandonment and eventual replacement of such machines. The company is no longer in the business of making shell forming presses.
The Herrmann ""199 patent also describes an end manufacturing process performed on a sheet of end material. In particular, a sheet of material is fed into the press, and initial forming operations and lancing of a press tab opening feature are performed. Then, the end is blanked. The blanked ends are then fed to downstream work stations, where various additional forming operations are performed on the ends. The Herrmann ""199 patent was commercialized for a short time, but such machines were soon abandoned and replaced.
During the mid-to-late 1980s, the art moved away from systems that attempted to form a complete end in a single machine, as typified by the Herrmann and Buhrke patents. The art adopted a two-stage type of system using a shell press that formed shells from a coil of stock material, and one or more end conversion presses that converted the shell into a finished end. A representative prior art shell press and end conversion system is illustrated schematically in FIG. 1. The system of FIG. 1, described below, was a much more complex and capital-intensive system than those systems used previously. However, the increased capital investment required to build an end making line such as shown in FIG. 1 was believed justified since the system proved to be more reliable, required less maintenance and down time, and was capable of operating at higher speeds to produce more can ends per minute than prior systems.
The end manufacturing system 10 of FIG. 1 operates as follows. A coil stock feed mechanism 12 supplies a continuous sheet of end material (e.g., aluminum or steel), to a shell press 14. The shell press has a set of tools that form a shell in the sheet of end material and blank the shell from the sheet. Shell presses such as shown in FIG. 1 are made by companies such as Formatec Tooling Systems, Inc. and Redicon Corp. and are well known in the art. The shell press 14 in the instant example is a twenty four-out press (i.e., it forms twenty four shells in the sheet of material a direction transverse or oblique to the direction of movement of the sheet in the press). Shells are ejected out both sides of the press 14 and sent to curlers 16, where an edge curl is formed in the periphery of the shell, resulting in the shell 15 shown in FIG. 1A.
After curling, the shells are placed in stick form and moved along track work indicated at 20 to a balancer 22. The balancer 22 is a robotic distribution machine. It is needed because the curlers 16 are supplying shells along six sets of track work 20, whereas in the downstream direction there are only four sets of track work leading to four liner machines 24. The balancer 22 is used to collect the ends and appropriately distribute them to track work leading to the lining machines 24. The lining machines 24 add a compound liner to the shells. The lining machines supply the shells to a drying machine 26 (if a water-based compound is used), which dries the compound liner with forced air. The drying machine 26 is not needed if a solvent-based compound is used.
The drying machines 26 supply the shells along another set of track work 30 to a second balancer 32. The balancer 32 supplies shells in stick form to three sets of track work 34, 36 and 38 leading to three separate shell conversion presses 40. The conversion presses 40 take the shells of FIG. 1A and complete the formation of the end features in the shell. The conversion presses 40 also have a set of tools that receive a continuous sheet of tab stock from a source 42 and form tabs in the tab stock. The conversion presses 40 attach the tab to the shell, complete the formation of the ends, and supply the finished ends to three sets of track work 43 leading to three bagging stations 44. The converted ends are bagged in stick form and loaded on pallets for distribution to the site where the cans are filled with product.
The conversion presses 40 of FIG. 1 are also known in the art and commercially available from Stolle Machinery Inc., Dayton Reliable Tool and Mfg. Co., and Service Tool Company, among others. They are also described in the patent literature. See U.S. Pat. Nos. 3,886,881, 4,732,882; 4,568,230, and 4,640,116, the contents of each of which is incorporated by reference herein. The tab presses for forming tabs in the sheet of tab stock are also known and commercially available. See, e.g., the Stolle Conversion System 8 shell conversion press available from Stolle Machinery Inc., and the above referenced ""230 patent.
The conversion presses 40 of FIG. 1 all work in the same fashion. They incorporate a series of work stations having tools that complete the formation of an end from a shell 15 supplied from the balancer 32. The details of the work stations and forming operations performed on the shell will depend on the type of end and the requirements of the customer.
A representative embodiment for producing an end for a beverage can in the conversion press will be described for purposes of example. The operation of the first station in the shell conversion press 40 of FIG. 1 is shown in FIGS. 1B and 1C. A bubble 50 is formed in the center of the panel 52 of the shell 15. The bubble is the first step in the formation of a rivet that is used for attaching a tab to the end. At the second station, the bubble 50 is reformed to reduce the radius at 54 as shown in FIGS. 1D and 1E. At the third work station, the bubble is reformed a second time with a smaller radius at its base to allow the tab to be seated closer to the panel 52, as shown in FIGS. 1F and 1G.
At the fourth station, indicated in FIGS. 1H and 1I, the shell 15 is scored 56 to define an opening in the shell and a C-bead or a D-bead 58 is formed in the center of the panel 52 to remove excess metal put into the area by the scoring process. At the fifth station, indicated in FIGS. 1J and 1K, the panel 52 is formed in the region 60, giving the end strength. Excess metal accumulated during previous forming operations is pulled out. At the sixth station, indicated in FIGS. 1L and 1M, a tab 62 is cut off from its web, superimposed on the bubble/rivet 50, and riveted to the end. At a seventh station, indicated in FIG. 1N, the edges of the tab 62 are wiped down in regions 64 to remove sharp edges from the tab. Finally, in the eighth station of FIG. 1O, the end is either embossed or incised with lettering indicated at 66, depending on the customer requirements. This completes the formation of an end 70. The end 70 is then ejected from the press, placed in a stick of ends, and sent to a bagging station for bagging and loading on a pallet, as shown in FIG. 1.
The system of FIG. 1, while certainly capable of producing ends at high speed and in a reliable fashion, has several drawbacks. First, an enormous capital investment is required to install a system such as shown in FIG. 1. In particular, a large amount of expensive track work is required. The system requires two balancers and a total of four presses, all of which are very costly machines. Further, the layout of the equipment requires a large amount of space and therefore a large building site, which increases the cost. Construction of such a building and providing heating and cooling also increases costs. Furthermore, the sheer number of presses and the balancers results in a system that consumes a lot of electrical power during operation, and a large number or operators and mechanics, increasing the costs further. While the system of FIG. 1 could be modified somewhat by reducing the number of conversion presses or eliminating the dryers, the basic architecture of the prior art system based on shell presses, conversion presses, balancers and extensive track-work is a very capital, space, energy and labor intensive system.
The present invention provides a substantial improvement over the end manufacturing system of the general type shown in FIG. 1. It also presents solves problems inherent in the Buhrke and Herrmann systems. As described below, the present invention provides for the formation of an end from a sheet of end material in a single press, thereby completely eliminating much of the track work, balancers, extra presses, and space and capital requirements of the system of FIG. 1. Furthermore, there is no need for any balancers in the present system since there is only one press and the ends are fed directly from the curlers to the liners and to the bagging station. The cost savings to install a new end manufacturing system of the present invention, as compared to a new end making system in accordance with the prior art approach of FIG. 1, with the same capacity, is in the order of many millions of dollars. Further, the end making system of the present invention is particularly suitable to smaller scale implementations, but can be modularized to increase capacity without requiring substantial increases in floor space or capital investment.
In one aspect of the invention, an end manufacturing system is provided. The system includes a source of a sheet of end material, such as aluminum or steel in coil form. The sheet of end material is supplied to a press. The press has a series of work stations that perform forming operations on the sheet of end material so as to form a complete end in the sheet material. The curling of the end can be either performed in the press or, more preferrably, in a curler machine after the end is ejected from the press. As the sheet of end material is fed through the press, the work stations work on the sheet to form the end, and, at the same time, maintain the sheet of end material in a substantially continuous and void-free state. The feature of maintaining the sheet in a substantially continuous and void free state allows the sheet to be advanced through the press in a precise and controlled manner. This results in maintenance of proper alignment of the sheet with respect to the tools as the end is formed by the work stations. Accordingly, the press can be operated at high speeds and in a reliable fashion. Also, this feature avoids the registration, elasticity and misalignment problems found with the prior art system, such as the Buhrke press, that attempted to make a complete end from a web or sheet in a single press. The press includes a station that blanks the ends from the sheet when the formation of the ends is complete. The ends are then ejected from the press.
In a preferred embodiment, the work stations are organized such that the operations traditionally performed in a conversion press are performed first, and with the shell forming operation performed in the very last step. This is essentially the reverse of the previous technique of forming the shell first and then converting the shell into a end by adding all the end features, such as rivet, tab, pour panel, embossing, etc. By performing the operations on the sheet in the order provided by this invention, the sheet of end material is more readily indexed through the press in a controlled and reliable manner at high speed.
In an embodiment in which the curling is not performed in the press, the ends are fed to a curler station for curling the ends. The ends are then fed to a compound station applying a compound sealant to the ends. The ends are then fed to an inspection station and then to a bagging station for packaging the ends and loading on a pallet or other suitable structure.
In another aspect of the invention, a method of manufacturing can ends is provided that comprises the steps of introducing a sheet of end material into a press, and feeding the sheet of end material to a series of work stations in the press. The sheet of end material is worked in the series of work stations in a sequence of operations so as to complete the formation of an end in the sheet of end material. In contrast to the prior art approach described in the Buhrke and Herrmann patents, during the working of the end material the sheet of end material is maintained in a substantially continuous and void-free state. This permits the sheet feed mechanism to provide precise movement of the sheet relative to the work stations, and maintain registry of the sheet relative to the work stations as the sheet is fed through press. The method continues with the step of blanking the end from the sheet after the formation of the end has been completed. The ends are then ejected from the press.
The series of work stations in the press preferably include at least one station for forming a rivet in the sheet, a station for scoring the sheet so as to form an opening feature in the sheet, and a station for attaching a tab to the rivet. The stations may be arranged in said press such that the sheet of end material is fed through said stations in that order, fed to said blanking station, and then ejected from the press. The press can be a one-out press, that is, form only one end in a transverse orientation or at an oblique angle with respect to the direction of travel of the sheet. Alternatively, the press can be set up as a multiple-out press, such as a four-out press in the preferred embodiment.
The system of the above type can be readily implemented without the need for any balancers. The amount of expensive track work required is dramatically reduced. The separate shell press is eliminated. Since only one press is used per line, it results in a more compact arrangement. While a line with one press such as described herein may produce a smaller number of ends than a system say of FIG. 1, it could be implemented with a much reduced capital expenditure and investment. The system is a much more compact in terms of footprint, and can be installed in a smaller plant. All of these factors add up to a dramatic cost saving for installation of a new end manufacturing line.
As a result of the reduction in equipment needed to produce the ends, the maintenance and tooling costs are reduced. The equipment is easier to work on and simpler by design. It is even possible to modify an existing conversion press to that of the press of the present system by changing the tooling and the feed mechanism, without having to design an entirely new press from scratch. The energy costs are less since there is less equipment running.
Several other advantages are obtained by the system of the present invention. The system is easier to work on than existing shell and conversion systems, and it is easier to change the end diameter. The system is particularly suitable for niche markets and special end requirements.
Further, because there are no balancers, and no elaborate shell or end track work and distribution schemes such as shown in FIG. 1, there is complete traceability in the system. If a particular problem is found with an end at an inspection station at the end of the line, the problem can be traced to the particular tool or even portion of a tool in the press.
Furthermore, since the press is not working on individual ends, as is the case with a conversion press, but rather on a sheet of stock material, the press can operate on a shorter stroke. This, in turn, allows the press to run at faster speeds and produce more ends per minute than a system of similar space and capital requirements. Also, random orientation of the tooling relative to the grain in the end material, found in the prior art conversion presses, can be controlled since the ends are formed while maintained in a sheet of material (and not on individual shells), and the orientation of the grain relative to the press can be controlled by how the sheet is fed into the press. The grain of the sheet can be compensated for in a reliable and repeatable fashion by slight modification to the tooling. This, in turn, lowers the standard deviation of push, pop and buckle phenomenon in the ends and results in higher quality ends.
These and many other features and advantages of the invention will be more apparent from the following description of a presently preferred embodiment.